A hot spot is Elliott Bay, particularly off Myrtle Edwards Park. But the phenomenon also has been documented off Tacoma, Bremerton and Everett and in Port Susan, most commonly near combined discharges of stormwater and raw sewage. Further tests are planned, but so far not all of them have been funded.

Scientists wonder whether the effect is caused by hormones in women's urine or birth control pills. They also want to know more about substances known as surfactants, used in soaps, detergents, shampoos, cosmetics, sunscreens and other products. "We really don't know," said Sandie O'Neill of the state Department of Fish and Wildlife.

Industrial chemicals also appear to be interfering with fish reproduction.

Scientists say chemicals widespread in urban areas of the Sound have been known elsewhere to inhibit the growth of testes, reduce sperm production and quality, and cause "intersex fish."